1. Field of the Invention
The present invention relates generally to cables and support devices. More specifically, the invention is an energy absorbing high impact cable device which absorbs kinetic energy of rolling rocks upon impact within a rock fall net system.
2. Description of the Related Art
A variety of energy absorbing devices have been devised for minimizing shock or impact in a number of different application. Generally, the notion of shock absorbers have been relegated to use only in automobiles or similar vehicles for improving the comfort level of passengers, and reducing structural wear in the suspension systems of vehicles. This is a far cry to the use of such devices as herein described for applications involving rockfall fence systems.
Rock fall fence systems are used to protect motorists from rocks and boulders dislodged from slopes near roadways. Rocks and boulders can roll onto the road at high speeds carrying significant energy. There are many such rocks or boulders above and adjacent unprotected roadways here and abroad, that have caused fatalities and other damage. However, there has not yet been devised a cable device which absorbs large magnitudes of impact energy as herein described. While various devices have been developed for attenuating or absorbing shock induced impacts, these devices alone have been proven insufficient for preventing fatalities and great damage including structural deformation associated with rolling rocks and boulders.
For example, U.S. Pat. No. 3,380,557 issued to Peterson discloses a variable kinetic energy absorber comprising a piston and a cylindrical tube wherein a plurality of different plastic materials are used to minimize material deformation from a compressive force. The plastic materials are placed within the cylinder to give different resistive forces to extrusion at different positions of movement of the piston.
U.S. Pat. No. 3,553,345 issued to Edwards discloses a vibration damper comprising a wire conductor, a bell shaped damper which rests on the conductor, and is mechanically fastened thereto. A rod extends the length of the wire conductor and is in mating attachment between the conductor and damper. This particular damper is designed for overhead transmission line conductors, ground wires, guy wires, etc. for reducing eolian vibration and galloping or dancing wires.
U.S. Pat. No. 5,207,302 issued to Popp et al. discloses a shock absorbing tube used for rock wall fences in particular. The tube is bent to form a loop or ring with ends overlapping. A sleeve or clamp retains the form of the loop and allows the tube to slide therethrough while under tension. Another U.S. Patent issued to Popp et al. (U.S. Pat. No. 5,321,922) discloses a similar loop cable construction, except a plastic material extends completely around the cable and partially in the ground when the steel cable is used as an anchor for securing netting panels against falling rocks and avalanches. The following Foreign Patents and document(s) by Bollinger (CH 610 631), Enzler et al. (CH 659 299) and Cargnel (WO 87/00878), respectively teach similar loop like dampers as taught by Popp et al.
Other U.S. Patents disclosing shock absorbing mechanisms or devices are those by Duncan (U.S. Pat. No. 5,332,071), Fohl (U.S. Pat. No. 5,340,152), Ellis et al. (U.S. Pat. No. 5,433,290), Young (U.S. Pat. No. 5,535,861) and Eicher et al. (U.S. Pat. No. 5,597,017); these are directed to safety line cables. The safety cable taught by Duncan, in particular, comprises a cylindrical container having a spring like damper disposed therein. The cylinder plastically deforms under the impact load of a falling worker to indicate activation.
U.S. Patents issued to Morely et al. (U.S. Pat. No. 3,917,030), Ege (U.S. Pat. No. 4,530,205), Seiler et al. (U.S. Pat. No. 4,530,205), and Kopanakis (U.S. Pat. No. 5,669,214) are generally relevant to the energy absorbing high impact cable device according to the invention in that they disclose high energy absorbing articles and methods of making the same. The various materials disclosed in each referenced patent principally serve to limit stress propagation or bending strain.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus an energy absorbing high impact cable device solving the aforementioned problems is desired.